Table of Contents
Advertisement
Model 4 12A
h. Turn 412A ON and allow 30-second warm-up
period.
Observe de voltage amplitude on
oscilloscope.
i. Move oscilloscopc input (with series resistor) to
Modulator output at junction of green lead from
Modulator and C104 (0.01 Microfarads).
j.
Waveform should be similar to that shown in
Figure
5-5.
Peak-to-peak amplitude should be
approximately equal to dc voltage observed in step
h. Signal frequency sliould be
5/6
power line
frequency.
k. If waveform is not satisfactory, check chopper
motor and assembly or Modulator and input
circuit as indicated by deficiency in waveform.
p - 2 0 MSEC-
--)1
Figure 5 5 . Modulator Waveform
5-34. MODULATOR REPLACEMENT.
5-35.
The photoconductor cells in the Modulator
(VllOA/B) are not separately replaceable. If a cell is
defective, the Modulator block assembly should be
replaced, using the following procedure.
a. Disconnect 412A from power source and remove
cabinet.
C O N T A M l N A T I O N
O R
FINGERPRINTS ON THE RANGE
S W I T C H O R COMPONENTS
MOUNTED ON THE RANGE
S W l T C I I
M A Y
K E D U C E
A C C U R A C Y
O F
T H E
INSTRUMENT.
b. In 41 2A cabinet model, remove side shield.
c. Note and record color code of wires before
removing from Modulator assembly printed circuit
board.
001
29-5
Section
V
d. Remove four screws holding light-beam chopper
assembly. It is not necessary to disconnect wires.
e. Spread grip rings on Modulator light rods and slide
rods out of Modulator block.
f. Remove four screws holding modulator assembly
to
chassis.
NOTE
Be sure to seat the four insulating
shoulder washers in mounting holcs
when replacing the assembly.
g.
Lift out Modulator assembly. If it is necessary to
replace Modulator block asscmbly only, rcmovc
four screws holding printed circuit board to block.
Note color and location of wircs between block
and printed circuit board before disconnccting.
5-36. DEMODULATOR CHECK.
a.
Disconnect 412A from powcr sourcc and removc
cabinet.
b. Remove V102 (on Amplifier Assembly).
c. On iight-beam chopper assembly, rcmove uppcr
lamp nearest front of instrument. This lamp
illuminates
VI
1
I
A.
d. Connect a 1.0 microfarad capacitor across input
terminals of test ohmmeter.
e. Connect test ohmmeter common lead to
Demodulator terminal with pinklorange wirc.
Sec
Figure
5 6 .
f. Connect other test ohmmeter lcad t o tcrminal
with whitelorange wire.
g.
Connect 412A to power source and turn ON.
.
h. Resistance indicated on test ohmmeter should bc I
to 2 megohms.
i. Turn
41 2A
OFF.
j. Replace lamp in light-beam chopper and remove
upper lamp nearest rear of instrument. This lamp
illuminates
VI
I
1
B.
k. Connect test ohmmeter common lcad to
Demodulator terminal with brownlorange wirc.
5
-7
Advertisement
Table of Contents
